This invention relates to a continuous process and apparatus for producing quick cooking (instant) rice and vegetables. Rice or vegetables produced in accordance with the present invention would require only above five minutes contact in hot, not necessarily boiling, water for swelling to make the rice or vegetables suitable for consumption, while retaining most of the nutritional value in the rice or vegetables.
Standard milled white rice and vegetables, such as potatoes, carrots, peas, corn and the like generally require about 20 to 35 minutes of cooking in boiling water before consumption. In addition to the long cooking time required for rice and these vegetables, the starch in rice and some of these vegetables is sometimes not entirely gelatinized. In the case of rice and some conventionally prepared vegetables, an undue number of the starch cells in the rice or vegetable may burst to form a viscous, sticky, pasty cooked mass. For these reasons and others, the consumption of rice and certain vegetables has been restricted for many years. Accordingly, considerable effort has been directed towards the production of quick cooking rice and vegetables.
Generally, "quick cooking rice" has been defined as rice that has been hydrated and/or gelatinized to various degrees and dried in such a manner to produce individual kernels for subsequent cooking in boiling or hot water for a short period of time.
An excellent discussion of quick cooking rice is given in RICE CHEMISTRY AND TECHNOLOGY edited by D. F. Houston, published by the American Association of Cereal Chemists, Incorporated, St. Paul, Minn., Chapter 15, Quick Cooking Rice, Robert L. Roberts, pages 381-399.
Generally most prior art methods of making quick cooking rice involve soaking in the rice in water. For example, see U.S. Pat. Nos. 2,438,939; 2,733,147; 2,740,719; and 2,828,209. The soaking technique, however, is time consuming, involves a loss of valuable rice starch and produces a waste water pollution problem. Soaking involves the use of excess water which invariably leads to a dissolving of rice starch into the water which not only lowers the nutritional value of the rice (loss of carbohydrates and calories), but also results in the production of a starchy water effluent which must be disposed.
Another technique used in producing quick cooking rice involves fissuring the rice and such method is disclosed in various patents including U.S. Pat. No. 3,157,514 and Norwegian Pat. No. 107,170. U.S. Pat. No. 3,157,514 suffers from the fact that it specifically requires hydrated rice to be used as a raw starting material. Further, U.S. Pat. No. 3,157,514 involves the soaking technique and cooling the rice before drying (a very energy wasteful step). The rice product of U.S. Pat. No. 3,157,514 is not completely gelatinized and thus requires boiling to render the rice suitable for consumption. Th rice produced by the method of Norwegian Pat. No. 107,170 is also not completely gelatinized and thus requires boiling in water before consumption.
Still another process to produce quick cooking rice is given in U.S. Pat. No. 2,937,946 which discloses the use of spraying with hot water to gelatinize the rice. This technique requires large amounts of hot water and is thus very energy consuming. Also, the process of U.S. Pat. No. 2,937,946 involves a great deal of time to achieve gelatinization.
Although less attention has been focused on the preparation of quick-cooking vegetables, there has been some progress in this field.
Several patents describe processes for pre-cooking potatoes. Exemplary of these patents are German Pat. Nos. 743,714 and 833,441; and German Offenlegungsschrifts Nos. 1,946,129 published Oct. 1, 1970 and 2,856,764 published July 12, 1979; Swiss Pat. No. 590,617; Norwegian Pat. No. 134,683; United Kingdom Pat. No. 2,008,383; and U.S. Pat. Nos. 3,038,813; 3,410,702 and 3,635,729. The soaking of peas and beans in water prior to cooking is described in U.S. Pat. Nos. 1,813,268; 1,859,279; 3,291,615 and 3,388,998.
The drying of gelatinized rice and vegetables usually places a great strain on the rice or vegetable resulting in the deterioration of its cell walls. The more times rice or the vegetable is dried, the more cell walls are destroyed. The result is that the rice or vegetable loses its capacity to reconstitute and reshape to its original form when soaked in water. Experience shows that for rice and vegetables that are dried several times, the ability to reconstitute is reduced by 40% to 60%. On the other hand, for rice and vegetables which have been dried only once, the ability to absorb water and reshape is reduced only by 5% to 10%. It is therefore important to find a method that provides suitable water absorptivity for sufficiently dried rice and vegetables.